Question

The potential difference applied to an X-ray tube is 5 kV and the current through it is 3.2 mA. Then the number of electrons striking the target per second is

• A. $ 5 \times 10^6$
• B. $ 2 \times 10^{16}$
• C. $ 1 \times 10^{17}$
• D. $ 4 \times 10^{18}$

Answer 1

Answer: (B)

Given, potential difference, $V = 5\,kV$ and discharge current, $I = 3.2 \,mA = 3 . 2\times 10. 3\, A$
As, We know that current, $I = \frac{ne}{t}$
where, $n =$ number of electron, $e =$ charge on electron and $t = $time
$\Rightarrow n = \frac{It}{e}$
Putting $ t= 1\,s$ and $ e = 1.6 \times 10^{-19} C$
$\Rightarrow n = \frac{3.2 \times 10^{-3} \times 1}{1.6\times 10^{-19}} = 2 \times 10^{16}$
Hence, $2 \times 10^{16} $ electrons are striking the target per second.